Once upon a time, people worked closely with nature in order to survive. A farmer’s work regimen was ordered by the changing seasons, hunters searched for signs to tell them when to hunt, and fishermen tracked the moon and tides to bring in the best catch.
Nowadays, unless we make the effort to feel the sun or watch the clouds, we might go days and weeks without tuning into nature at all. Even though we miss the small changes, even the most distracted of us will notice the spring greening of trees at bud-break and their luminous glow in the fall. We’ll tune in for hurricanes, droughts, blue moons and the promise of snow. And no matter how rushed or harried we may be, the sign of a v-formation or the distant honking of geese will make us stop for a moment to gaze at the sky and wonder what irresistible force compels those birds to fly south once again, for the winter.
Bird migration is one of those intriguing events that we try to understand and try to define with neat explanations. As with many of nature’s mysteries, however, there are no neat explanations. Some bird species don’t migrate at all, and even among those that do, there are individuals sometimes, within a migrating species, that stoically stay put while their fellow birds take off! Perhaps this is nature’s way of “hedging her bet” in the event of some catastrophic climatic upheaval. Although scientists have developed some plausible theories about migration, they haven’t yet grasped all the intricate details of this winged cycle.
Of those birds that do migrate, most travel north in the spring to find hospitable meeting grounds, and south in the fall as northern food supplies become scarce. Many of them will follow the same route; and some will even return to nest in the same place year after year! What is less clear is how this pattern developed.
One explanation points to a process called niche exploitation. As glaciers retreated after the last Ice Age, birds ventured into enticing new lands with promising food sources. Drawn further and further north by bountiful summer vegetation, birds would have needed to return to the south as the summer waned and food supplies dwindled. Perhaps, the repetition of this yearly routine evolved into the urge to migrate.
Birds generally follow a north/south migration route with the areas of heaviest travel following coasts, mountain ranges, and major river valleys. They appear to navigate using the position of the sun and stars, polar magnetism, landmarks, the direction of the wind, and distinctive smells. Some birds fly non-stop for days without stopping to rest or even eat! Others take a more leisurely trip and touch down for days, weeks, even months along the way.
Birds that like to stop awhile appreciate areas like ours that have large areas of wetlands. Wetlands – marshes, swamps, and bogs – are the link between water and land. They provide water, shelter and an abundant food supply for the estimated 80 percent of the world’s bird species that inhabit wetlands. New Jersey’s 1.5 million acres of Pine Barrens encompasses both wet lowlands and drier uplands where native bird-friendly trees and shrubs like Red Maple, Pitch Pine, River Birch, Bayberry, Serviceberry, Red Cedar, Black Gum, Sweetgum, American Holly and Oak offer nesting, sheltering and feeding opportunities for many bird species.
Migrating is generally an arduous and risky business, but the threat of bad weather or hungry predators is nothing compared to the human threat of loss of habitat. As we develop land to house, service and entertain ourselves, we destroy the space that birds need to rest and feed during long journeys. In our own backyards, however, we can help repair the damage by planting trees and shrubs that will provide nesting space, protection from predators, and food sources that are naturally programmed to ripen just as those weary migrators stop by to rest.
Specific trees are sought by specific bird species for nesting materials, nesting locations, and food sources. For instance, American Goldfinches, Eastern Meadowlarks, and Yellow-breasted Chats seek our Birches and White Pine, while Red-winged Blackbirds look for Serviceberry and Eastern Red Cedar. And if you want to invite Blue Grosbeaks to your yard, go for the Crabapples, Sweet Gums, and Willows, but if you’re on a quest for the elusive Indigo Bunting, put in some nice Mulberry or Elderberry instead.
Living Landscapes can steer you in the right direction in choosing the trees and shrubs that warmly invite birds to spend some time in your yard.